Author Topic: Vibrato problem on a 140 (Varistors)  (Read 1565 times)

Offline FixerUpper

  • Fiesta Red
  • **
  • Posts: 23
    • View Profile
Vibrato problem on a 140 (Varistors)
« on: November 11, 2012, 12:45:54 PM »
OK. So I did something really stupid.  On the 140 they had this Amphenol plug the went from the power source to the battery pack which is just for the pilot light. I suppose it has some other purpose but I dont ever plan I using the battery pack (whatever that is). I thought I could get rid of the external wire and plug by hard wiring it under the chassis. To do this correctly I needed to wire a jumper from pin 6 of the battery pack plug to pin 2 of the 4 pin power plug. Unfortunately I had a bit of brain freeze and I wired it from pin 6 of the battery pack plug to pin 6 of the control plug. I suppose I was fixated on pin 6. Anyway, the problem is that pin 6 of the control plug goes to the vibrato pot. Now I have no vibrato but luckily everything else works. I have gone through everything and all the transistors still seem good and I'm still getting a reasonable signal to the base of transistor 5 which controls the varistors. Also, doing a basic diode test transistor 5 still seems good. But the emitter and collector of transistor 5 don't seem to be putting out a signal of any sort when checked with the oscilloscope. These both connect to varistors.

My question is, do you think the varistors could have blown even though everything else still tests out as good? I couldn't find any shorted caps or anything like that.

My second question is, somewhere on this form I found that the markings on replacement varistors from Morelock's is V14K / VEI 130. I typed V14K into Mouser and came up with this:

http://www.mouser.com/Search/ProductDetail.aspx?R=ETFV14K130E2virtualkey59250000virtualkey871-ETFV14K130E2

It is a combination varistor and fuse but it has connectors that allow you to ignore the fuse. I'm willing to give it a shot just to see if they will work (and dispell the belief that they are extremely rare if they do work) but would this just be a complete waste of time?

Any input would be appreciated. I attached the schematic for anyone interested. I also attached the manual which describes the vibrato circuit in the second paragraph on page 24 (according to adobe) or page 3 (according to what it says at the bottom of the page. but these are out of order)


One more question: The transistors in this are GT 2477. I can't find any information anywhere. Can someone recommend a replacement?

Even if no one responds, thanks for reading this far!

Jim

Offline FixerUpper

  • Fiesta Red
  • **
  • Posts: 23
    • View Profile
Re: Vibrato problem on a 140 (Varistors)
« Reply #1 on: November 12, 2012, 10:05:29 PM »
Well Morelock's got back to me and said they are sold out. I'm waiting for the ones from Mouser. I'm not too hopeful they will work but who knows I might get lucky.  If anyone has any tips for me on how to get this working it would be appreciated.

Offline pianotuner steveo

  • MIDI Mark V
  • *****
  • Posts: 3166
  • A keyboard player in love with vintage guitars!!!
    • View Profile
Re: Vibrato problem on a 140 (Varistors)
« Reply #2 on: November 13, 2012, 08:38:12 AM »
The only model I remember ever having a battery pack was the 200b......
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline FixerUpper

  • Fiesta Red
  • **
  • Posts: 23
    • View Profile
Re: Vibrato problem on a 140 (Varistors)
« Reply #3 on: November 13, 2012, 09:28:18 PM »
The 140 has a six pin plug on the back of the piano that is labeled as battery pack. On the schematic it is labeled "Battery Pack Tone Cabinet". I think it was for connecting some sort of external amplifier.

Offline FixerUpper

  • Fiesta Red
  • **
  • Posts: 23
    • View Profile
Re: Vibrato problem on a 140 (Varistors)
« Reply #4 on: November 14, 2012, 11:05:02 PM »
in case anyone is interested the replacement varistors worked.

Offline FixerUpper

  • Fiesta Red
  • **
  • Posts: 23
    • View Profile
Re: Vibrato problem on a 140 (Varistors)
« Reply #5 on: February 15, 2013, 11:28:21 PM »
Vibrato is not working now. I don't know if someting else went or if I was just imagining it working.

Offline DocWurly (formerly Paleophone)

  • Vendor
  • Mark I
  • *****
  • Posts: 355
    • View Profile
    • DocWurly.com
Re: Vibrato problem on a 140 (Varistors)
« Reply #6 on: October 23, 2018, 12:07:24 PM »
Does anyone have a source for the GT-2477 transistors --or an equivalent-- in the 140 amps?  I think I blew one.